Need advice on a tough situation.

I am pregnant with my second child I found out yesterday. I am super excited we were trying since my baby turned 1, so 9 months. Well my sister in law is due in July with her 4th hoping for a girl since she has all boys. My other sister in law has been trying for 2 years and has had trouble and health issues they recently asked her to stop trying for atleast 6 months. My heart aches for her since we've grow. Super close lately. She was unbelievably bummed about her sister being pregnant and I am totally just afraid to tell her. I want her to be the 1st person I tell because I know I want her to know before everyone else to deal with it. I just don't know how she will react and I don't want to hurt her. Any thoughts or advice?